Orchid culture / Rivermont Orchids.

ORCHID CULTUR

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i Preparedpiiecollaborations with Dr Gavino Rotor. Jr,
Department or Eloriculture and Ornamental Horticulture;
Cornell University."'

O R CH ID §$
SIGNAL MOUNTAIN, TENNESSEE

In this discussion we answer a few basic questions about orchid
culture by briefly discussing the most important factors of the
environment that influence the growth of orchids. Since climatic
conditions vary a great deal from place to place andat different
timesofthe year, specific instructions are inadvisable. Rather,
it would profit the grower to gain an idea of how various factors
affect plant growth and how theyare relatedto each other. Thus,
he will be able to act intelligently, to analyze any problem that
may arise, or to interpret any recommendation as they applyto
his own situation.

Repotting is specifically described to serve as a guide for

beginners.

Reference may be made to some of the fine books on orchid
culture listed in our bibliography.

WATER

Water is used by plants in the manufacture of plant food, in
transporting the food to various parts of the plant, and to keep
the plant erect by making the cells turgid. One can very well
imagine what would hapen if a condition of water deficiency
should occur. The cell walls would lose their rigidity, leaves
and pseudobulbs would become shriveled, and the manufacture
andtransport of food would cease. Growthand development would
be slowed down considerably and eventually cease.

Roses, chrysanthemums and many other garden plants wiltas
soon as water becomes unavailable. With Cattleyas, onthe other
hand, the effect of insufficient water is not immediately obvious,
although internal changes may have occurred. The effect of lack
of water is not immediately shown by the succulent and much-
thickened pseudobulbs and leaves. Drying the osmundine thorough-
ly between applications of water could actually be harmful to the
growth of Cattleyas.

Most of the water loss from plants is lost through transpiration,
Transpiration simply means the loss of water from plant tissues
spethemrounimo @ovaltetmvapot. abl Getermining the trequency of
watering, the factors affecting transpiration should be considered.
These are discussed in the following pages.

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TEMPERATURE AND LIGHT INTENSITY

INTRECATION GO TRANSPIRATION. = Excessive light intensity
raises the temperature of the plants thus increasing the loss of
water from the leaves. If the rate of water loss is faster than the
rate of water intake through the roots, the plant will wilt. We see
here the danger of drying plants between waterings especially
under conditions of high light intensity.

When the sun isshining on the leaf, the leaf temperature is raised
above that of the surrounding air and plants lose water .to the
atmosphere even when it is saturatedwith moisture (100% relative
humidity). This is a proven and accepted fact. Obviously, the
best way to cut the excessive loss of water from the plantis to
coolthe leaves and the house so that there would not be much
difference between their temperatures. One way of doing this is
to increase humidity by spraying water over the plants, the walks
and benches. It has been found, however, that increasing the
humidity in this manner cools the house for less than 30 minutes.
The effect is so temporary since the water on the leaf surfaces
soon evaporates and the atmosphere itself gets dry again,
especially when there is good air circulation. Furthermore, so
long as the leaf receives light, its temperature will always be
higher than that of the surrounding air and hence, the plant will
continue to lose water regardless of humidity.

Shading prevents the sun's rays from striking the leaf andcools
the house, reducing the difference between the leaf and the house
temperatures throughout the day. Shading, therefore, is amore
effective way of reducing water loss than increasing humidity.

Spraying water is not only ineffective but a good way of spreading
diseases. High humidity and high temperature together createa
condition that is ideal for the growth of many destructive fungi
and bacteria.

IN RELATION TO GROWTH. Within certain limits and providing
Otherstactoranasmwater, light,. 6tc,, are, sufiicient, al rise in
temperature usually increases food production, respiration and
rate of growth.

The energy necessary for growth is given off in respiration, a
process which uses the food manufactured by the plant. If little
food is available, it is used up in a short time and growth ceases.
This situation is aggravated by low light and high temperature.
A plant may not grow at 40° F. because of the very low rate of

Pseudobul b--—-—

Rhizome -——

Beige

The stage of developing roots when the plant
isereadyvaforerepotling.

Li 2a eae ——Developing shoot
— ———-—-—-—-—-formant bud

big? 5:

A Cattleya plant with dormant buds and a
developing shoot.

respirationatthattemperature. A cool house orchid may not sur-
vive at 80° F. because it may respire so fast that the process of
food synthesis cannot keep up with the rate of respiration. If the
night temperature is too high during periods of poor light intensity,
growth becomes weakened, the flowers are smalland dark-colored
flowers become pale.

Generally, Cattleyas grow well with a minimum night temperature
of 60° F. or within a range of 58° to 65° F. Most growers keep
the day temperatures five to tendegrees above the night tempera-
ture during cloudy days and from ten to fifteen degrees higher
during bright days.

Light is necessary in the manufacture of food by plants. Aside
from other factors, there must be sufficient light for maximum
food production.

Many orchid growers have a tendency to shade Cattleyas ex-
cessively. This practice keeps down food production and slows
growth. A very low light intensity is especially detrimental at
high temperatures. Such temperatures are conducive to rapid
respiration and what little food is synthesized in the plant under
conditions of poor light is rapidly used in respiration. Cattleyas
receiving too little light have small, thin and weak pseudobulbs.
The leaves are thin, flop over andsometimes do not expand fully.
Increasing the light intensity not only promotesa strong, vigorous
top growth but also improves root growth; food production is
stimulated and more food becomes available for the proper de-
velopment of both top and roots. The amount of stored food in-
fluences flower production and the size, color, and texture of the
flowers.

Very high intensities, on the other hand, can reduce the amount
of chlorophyll in plants. Chlorophyll is the substance that is re-
sponsible for the green coloration of plants and which enables a
plant tomanufacture food. WithCattleyas, too much light results
in yellowing of leaves.

REGULATING THE LIGHT INTENSITY. Removing shade from the
glass in winter helps the plants to utilize all available light. The
shading material ordinarily used is easily washed off by rains so
that by winter there is hardly any left. Scrubbing may be neces-
sary where a more permanent type of shade has been used, as

lime and salt with oil, or white lead with gasoline. There are
several products on the market for cleaning glass.

In the home the maximum amount of light can be obtained from
south windows, and Cattleyas will grow well in this situation.

In most areas, shading is necessary in summer. An adjustable
shading system is the best way of getting the desired light inten-
sity. Some of the materials that maybe used are Venetian blinds,
roller lath shades on runners a foot above the glass, or cheese-
cloth with eyelets so that it may be drawnover the plants on bright
days and pulled back on cloudy days.

Shading compounds as white lead and gasoline may be sprayed on
the glass. However, this compound is difficult to remove. We
recommend our special Rivermont shading compound.

REGULATING THE TEMPERATURE. Heating and ventilation are
the most important methods of keeping the temperature within the
desiredlimits. Oil, natural gas, or electricity are popular sources
of fuel. The most economical heating can be obtained by the use
of hot water.

Thermostatic controls in both heating and ventilation can be very
practical. Their use has helped the grower who has to be away
during most of the day. On bright days, direct solar heat and
radiation cause the temperature to rise in the house. The heat
should, therefore, be turned off or the ventilators opened. In
winter, care should be taken to prevent cold air from rushing in.
Ventilators should be opened on the leeward side.

POTTING

A Cattleya plant needsrepotting when: (1) it has outgrownits pot;
(2) the osmundine has decayed toa point where it starts to fall
apart (indicated by its readily breaking off when a pinch is taken
between the fingers. ) These two conditions are ordinarily reached
after two years. When a plant has to be repotted, it is best to
wait until one or two roots start to develop from ,the base of the
lead.

Select a pot large enough to permit growth of two successive

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YOUR FIRST ORCHIDS AND HOW TO GROW THEM

Easy lessons on how to grow orchids in your home or greenhouse.

Itustrated in full color. Third and revised edition $1.25 postpaid.

ORDER FORM
RIVERMONT ORCHIDS

Signal Mountain
Te: nessee

I enclose $ Please send___t_.._____ copy (ies) @ $1.25 each

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growths when the butt of the plant is placed against the edge of the
pot.

REPOTTING SEEDLINGS FROM COMMUNITY POTS. For repot-
ting these seedlings 1-3/4"' and 2" pots are suitable. Run a dull
knife all around the inside surface of the pot and lift out the ball
of osmundine with all the seedlings. Separate the individual seed-
lings, carefully avoiding breaking the roots. Trim all the broken
root ends and place a piece of peat on each side of the plant, with
the top of the peat slightly covering the base of the plant. Next,
insert the plant with the osmundine inthe pot usinga small potting
stick, and pack more osmundine around the plant. Do not pack
hard but just firm enough to hold the plant in place under all cir-
cumstances. When finished, the osmundine surface should be
level and about 1/8"' from the top of the pot.

REPOT TING OLDERSEEDLINGS AND FLOWERING-SIZE PLANTS
The plant with the osmundine is lifted out of its pot as previously
described above. Next, trim the plant, cutting all of the dead
roots and dead or diseased pseudobulbs. Old, but healthy back
bulbs may be removed for propagation purposes; leave at least
four or five mature bulbs with the lead. Shake out or remove all
of the decayed osmundine. Fill one-thirdof the pot withpieces of
brokencrock. Holdthe buttof the plant against the edge of the pot
and place small pieces of osmundine next tothe plant in sucha way
that the rhizome is slightly and not completely buried inthe os-
mundine. Work in more and more pieces of osmundine until the
plant is very firmly held in place. The surface of the osmundine
should be about three-fourths of an inch below the top of the pot.
This makes watering easier.

CARE OF THE PLANTS AFTER REPOTTING. Water the osmun-
dine once thoroughly and place the newly-potted plants in a shady
location until the roots grow out; never allow the osmundine to dry
out completely. The frequency of watering, as previously pointed
out, depends on various factors. The plants may be given normal
light as soon as they are established.

Bibliography

ORCHIDS: THEIR DESCRIPTION AND CULTIVATION
Charles He. Curtis; Putnam & Co, Ltd:
42 Great Russell St., London
4 Pounds, 4 Shillings.

ORCHIDS ARE EASY TO GROW
Hebe Loganrandils Onmc OSper
Ziff-Davis Publishing Co., Chicago-N. Y., $6.00

HOME ORCHID GROWING
Rebecca T. Northern
D. Van Nostrand Co., Inc., $6.50

A.B.C. of ORCHID GROWING
John V, Watkins
Ziff-Davis Publishing Co., $3.00

AMERICAN ORCHID CULTURE
Edward A. White
Aver. De \UaMare Gom Nas 6200

ORCHIDS AND HOW TO GROW THEM
Adelaide C. Willoughby
Oxford Printing Co.; $3.50

YOUR FIRST ORCHIDS AND HOW TO GROW THEM,
Published by the Oregon Orchid Society, Inc., $1.00